It seems to be up the GM. The rules state:
Growing up, you were probably exposed to a Family Trade. Perhaps you learned your way around a forge from your father, who Game Masters: While this is ing on, you should be thinking about what type of scenario you will be placing the Adventurers in. It is the Game Master’s job to create a convincing setting and story for the Adventurers, which includes locations to visit, enemies to fight, and NPCs to interact with. Is this going to be a one-off adventure? Or are you planning to create an entire world for your Adventurers to explore? You can put as much or as little effort into this as you like, but keep in mind it’s your job to keep everyone on track and entertained. One-off adventures can be planned with a few minutes of preparation; however, if it is your goal to have a larger campaign in mind, this is going to take some work on your part to plan. Take some time to look through the For The Game Master section.was a smith. Maybe your mother was a weaver and taught you how to make and mend clothing. Whatever it was, you picked up some knowledge of this craft and gain Advantage in situations
where you can put it to use. Choose some sort of Family Trade for your character; your Game Master will then decide how it will be applicable during gameplay
So I'd interpret it in a way that gives the GM a lot of wiggle room on whether to apply the Family Trait to a specific situation.No hard rules to be found
